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U.S. Department of Health and Human Services


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Public Health Advisory: Colistimethate (marketed as Coly-Mycin M and generic products)


The FDA has received a report about the death of a patient with cystic fibrosis (CF) who used the antibiotic Colistimethate that had been premixed by a pharmacy into a liquid for inhalation with a nebulizer.  A nebulizer is a device that turns liquid medicine into a mist which is breathed in by patients to deliver the medication directly to their lungs.  Nebulizers are commonly used by patients with CF. The Colistimethate that was used by this patient had been prepared and dispensed by the pharmacy as a ready-to-use liquid.  

Colistimethate is FDA approved only for injection into a vein or a muscle; it is not FDA approved for use as a liquid to be inhaled via nebulizer.  When Colistimethate is mixed into a liquid form, the product begins to break down into other chemicals that can damage lung tissue.  Colistimethate is used to treat infections caused by certain types of bacteria, including the bacteria Pseudomonas aeruginosa, a germ that is known to cause serious lung infections in patients with CF. 

In light of this reported patient death, FDA offers the following recommendations:

  • If using the liquid form in a nebulizer, it should be used promptly after being mixed.
  • Patients should discard any unused pre-mixed liquid form of Colistimethate.
  • Healthcare professionals who use Colistimethate to treat patients with CF should be aware of the potential for serious and life threatening side effects from inhalation of pre-mixed, ready-to-use liquid forms of Colistimethate.  The side effects are as a result of local toxicity to the lung and airway. 
  • Healthcare professionals who treat patients with CF should work out a treatment plan with their patients that best meets their needs.
  • Patients and/or their caregivers with questions or concerns about this advisory should contact their healthcare provider or their Cystic Fibrosis Care Center to determine how best to continue treating their infection.

You can find more details about Colistimethate in the full prescribing information for Colistimethate.

The FDA urges both healthcare providers and patients to report side effects from medical products to MedWatch.  MedWatch reports may be made either online, by regular mail or by fax, using the contact information at the bottom of this page.


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